Maintaining patient body temperature at an acceptable level can be very important during some medical procedures because of the significant effect it can have on the outcome of the procedures. If a patient's body temperature is allowed to drop below an acceptable level, the patient could develop hypothermia which can prolong or complicate recovery. If a patient can be kept warm before, during, and after surgery, for example, then post-operative problems such as excessive bleeding, infection, shivering, and cardiac distress can be minimized. Maintaining the patient's body temperature in a surgical setting, however, may be difficult for a number of different reasons. One reason is that the operating room is typically air-conditioned at a relatively cool temperature to maintain air cleanliness and to provide the medical practitioners with a comfortable working environment. Another reason is that many surgical procedures require that at least a portion of the patient be exposed for surgical access. Such surgical access can further accelerate patient cooling if it opens up a large portion of the patient's body, such as the chest cavity. In addition, the onset of hypothermia during certain medical procedures may be accelerated by the patient's body position. For example, elevating the patient's leg to harvest veins for heart surgery may accelerate a decline in the patient's body temperature.
Cardiac catheterization is an invasive procedure in which the doctor threads a catheter through an artery in the patient's arm, groin, neck or leg to the patient's heart. A special dye is introduced into the catheter that allows the doctor to view arterial blockages with an x-ray machine to diagnose the patient's condition. The procedure often requires that a substantial portion of the patient's body be accessible to the doctor for comprehensive x-ray imaging to examine the various blood flows. As a result, much of the patient is exposed or only lightly covered during the procedure, which may cause the patient's body temperature to drop to undesirable levels. For this reason, it may be desirable to warm the patient during the cardiac catheterization procedure to prevent the onset of hypothermia.
Various devices exist for warming patients undergoing medical procedures. One such device pre-warms blankets placed over the patient. Another such device circulates heated air through a sealed blanket placed over the patient. Yet another such device circulates heated water through a sealed blanket placed over the patient.
There are a number of shortcomings associated with existing patient warming devices. The use of pre-warmed blankets, for example, can be expensive because the blankets are often disposed of after each use. Devices utilizing heated air have the additional drawback of circulating high temperature air in close proximity to patients who are often anesthetized. If a hot air duct associated with such a device inadvertently contacted an anesthetized patient, the patient could sustain serious burns before the practitioner or operator noticed the oversight and corrected the situation. In addition, all of these existing patient warming devices generally require high energy inputs to achieve the desired temperatures.
Another shortcoming often associated with existing patient warming devices is that most are configured to inefficiently warm the patient from the top down. This shortcoming often limits use of such devices to those portions of the patient where the medical practitioner does not require access. For example, if the patient is undergoing open heart surgery, then use of such devices would be precluded near the patient's chest. Unfortunately, however, in many surgical procedures the area where the practitioner is operating is often the area most in need of additional warmth.
A further shortcoming often associated with existing patient warming devices is a lack of adequate cleanliness. Body fluids, for example, can often get inside various parts of conventional patient warming devices when such devices are used in a surgical setting. These fluids can present cleanliness concerns for subsequent use of the device. This is one reason why many conventional patient warming devices incorporate disposable components. The use of disposable components, however, can increase the costs of surgical procedures.
Yet another shortcoming often associated with existing patient warming devices is an inability to adequately control the rate or level of patient warming. In certain circumstances, uncontrolled patient warming may complicate the surgical procedure or cause negative side effects in the patient.
Various products exist for monitoring patient egress from hospital beds. U.S. Pat. Nos. 6,307,168; 6,297,738; 6,025,782; and 5,623,760 to Paul Newham may disclose various aspects of such products. One such product includes a sensor coupled to a mattress that transmits a signal to a nurse's station when a patient moves off of the mattress and exits his or her bed. The mattress encloses a polyester fabric that supports two bands of conductive strands. The conductive strands can include silver plated nylon strands, such as those provided by Noble Fiber Technologies of 421 South State Street, Clarks Summit, Pa. 18411, that are woven into the fabric in a linear array. The two bands of conductive strands are electrically coupled to the sensor. When a person moves off of the mattress, the sensor detects a change in the capacitance between the bands and a signal is sent to the nurse's station indicating that the patient has exited the bed.